Posterior Sacroiliac Ligament, Posterior View

Description

Arising from the posterior iliac crest and posterior superior iliac spine, the posterior (dorsal) sacroiliac ligament spans inferomedially to the lateral crest and tuberosity of the sacrum, its oblique bundles crossing the back of the sacroiliac syndesmosis. The sacrum sits midline and posterior, bracketed laterally by the ilia, while the ligament fibers lie superficial to the sacroiliac joint capsule and deep to the dorsal musculature. Inferiorly, the ligament’s lower fibers approach the level of the sacral foramina and blend with the broader posterior ligamentous complex at the posterior pelvis. Landmarks stay clear. Posterior SI ligament anatomy matters because this is where load transfer from the lumbar spine into the pelvic ring is resisted during gait and single leg stance, and where palpation-based exam maneuvers attempt to localize pain near the PSIS. Sprain or degenerative change at the posterior sacroiliac ligament complex is discussed in mechanical low back pain and postpartum pelvic girdle pain, and it can be a pain generator targeted indirectly during SI joint injections or radiofrequency procedures by using the PSIS and sacral crest as surface and fluoroscopic references. For surgeons, the posterior view clarifies the ligamentous envelope encountered during posterior pelvic approaches and during fixation planning for pelvic ring instability. Faculty can drop this into gross anatomy and MSK anatomy teaching to contrast the posterior sacroiliac ligament with the interosseous and anterior sacroiliac ligaments, and to relate oblique fiber direction to stability of the joint. It also suits orthopaedic, sports medicine, and pain medicine materials that discuss SI joint examination, pelvic ring biomechanics, and referral patterns around the posterior superior iliac spine. Anatomical accuracy verified by SciePro's Medical Advisory Board.